(1) Field of the Invention
This invention relates to a polyolefin resin composition which is useful for industrial materials, particularly bumpers, instrument panels, and various trims of cars, various housings of light electrical appliances, and the like.
(2) Description of the Prior Art
Polyolefin resin compositions have been widely used mainly in the fields of car parts and light electrical appliances. In recent years, required various properties of the polyolefin resin compositions have become very high as the fields of the use have been widened. The blending of a thermoplastic elastomer has been practiced to improve the impact strength of polypropylenes. However, as a disadvantage in the method, there are problems, such as the decrease of the mechanical strength, rigidity, and heat stability. As a method to solve the problems, the blending of a fibrous or non-fibrous inorganic filler has been practiced. However, the reinforcing effect in the mechanical strength and the increase of the heat stability of the polypropylene blended with a non-fibrous inorganic filler are smaller than those of the polypropylene blended with a fibrous inorganic filler causing the appearance of flow mark or the deterioration of the external appearance in the weld. On the other hand, when a fibrous inorganic filler is blended, though the reinforcing effect in the mechanical strength is large, there occurs a silver streak surface roughness or a decrease in the impact strength. Also, the blending of a fibrous and a non-fibrous inorganic fillers in combination has been practiced without sufficient effects. Also, the combination of fibrous magnesium oxysulfate and other inorganic fillers has been proposed (cf. Japanese Patent Laid-open No. 227936/1984). However, in this method, when the fibrous magnesium oxysulfate is blended in a large amount or the molding temperature is elevated, a decomposition occurs to cause the silver streak and the deterioration of the external appearance.